Biophysical Characterization of Cancer Cell Phenotypes

Cancer is a serious health concern. Current treatments are limited due to certain subpopulations of cancer cells being resistant to chemotherapy and radiation. These subpopulations have been qualitatively identified but much work remains to quantify the abnormalities they exhibit such as irregular nuclear shape. This dissertation seeks to determine physical science methods which can identify and quantify the biological characteristics of cancer and non-cancer cells. For the first project, the deoxyribonucleic acid (DNA) and chromatin of cancer and non-cancer esophageal cells were quantified using spectrophotometry and atomic force microscopy. Then the cellular nucleus shape, chromocenters, nucleoli, and nuclear speckles were characterized using 3-D confocal microscopy. A majority of a cell's DNA is isolated in the supernatant fraction during salt fractionation for both cancer and non-cancer. Additionally, the nuclear size of cancer cells is roughly twice that of non-cancer cells due to the increased ploidy of the cancer cell line (more chromatin) and this chromatin exists in a less decondensed state than that of the chromatin in non-cancer cells. Then using combined atomic force microscopy and CLSM, the Young's modulus of cancer stem-like cells and non-stem-like cells were characterized for three breast cell lines: MDA-MB-231, MCF-7, and MCF-10A. It was determined that the MCF-7 is impacted by buffer environment whereas the MDA-MB-231 and the MCF-10A cell lines are not. MCF-7 cells are stiffer when measured in Phosphate Buffer Solution (PBS) compared to Hank's Balanced Salt Solution (HBSS) buffer possibly due to the fact that HBSS buffer tends to enhance the Warburg effect on cell lines. Additionally, there is a significant stiffness difference between stem cells and non-stem cells in the MCF-7 cell line which does not occur in the MDA-MB-231 cell line for the larger tip. These differences could be attributed to differences in cell phenotype for the cell lines. MDA-MB-231 cells are mesenchymal so it agrees with the hypothesis that there is no difference between cancer stem cells (CSCs) and non-CSCs cell stiffness; on the other hand the MCF-7 cell line is luminal so the CSCs being more mesenchymal-like would be softer than the non-CSCs.